Preheat oven to 400°.
Cut ends of eggplants and slice thinly, about 1/4” thick. Lay slices on a cooling rack and season with salt. Let sit for 20 minutes. Flip, season again, and let sit for another 20 minutes. Pat dry with paper towels.
In a large skillet over medium heat, heat oil. Sauté garlic for 1 minute, then add onions and oregano. Season with salt and pepper and cook until onions are translucent. Add marinara and cook until warmed through.
In a medium bowl, combine ricotta, Parmesan, egg and parsley. Season with salt and pepper.
In a 9“-x-13” casserole dish, spread a thin layer of marinara sauce, a single layer of eggplant “noodles“, a layer of ricotta mixture, then a layer of mozzarella; repeat layers. Top last layer of eggplant with marinara sauce, mozzarella, and Parmesan.
Cover with foil and bake for 35 minutes, then garnish with parsley and serve.
this site says to roast the eggplant first
“The eggplant roasts at 400 degrees F for 20 to 25 minutes”